I have seen the question "how do you add controls to TTabbedNotebook or TNotebook at run-time?" several times here and elsewhere. Well, after finally getting a few spare minutes to check into it, I have stumbled across the solution:

TTabbedNotebook

Adding controls to a TTabbedNotebook during design time is a pretty simple task. All you need to do is set the PageIndex or ActivePage property to the page you want to add controls to, and begin dropping the controls onto the TTabbedNotebook.

Adding controls to a TTabbedNotebook during run-time is also very simple. However, there is no mention what-so-ever in the Delphi documentation on how to do this. To make matters worse, the TTabbedNotebook source code is not included when you purchase the Delphi VCL source. Thus, we are left with a mystery. Fortunately, I have stumbled across the solution.

The first step to solving this mystery was to take a look at \DELPHI\DOC\TABNOTBK.INT, the interface section of the TABNOTBK.PAS unit where TTabbedNotebook is defined. A quick examination will reveal the TTabPage class, which is described as holding the controls for a given page of the TTabbedNotebook.

The second clue to solving this case comes from observation that the Pages property of TTabbedNotebook has a type of TStrings. It just so happens that Delphi's TStrings and TStringList classes provide both Strings and Objects property pairs. In other words, for every string in TStrings, there is a corresponding Objects pointer. In many cases, this extra pointer is ignored, but if you're like me, you're thinking "Ah-hah!"

After a quick little test in code, sure enough, the Objects property points to a TTabPage instance -- the one that corresponds to the page name in the Strings property. Bingo! Just what we were looking for. Now see what we can do:

The process of adding controls to a TNotebook is almost exactly the same as that for TTabbedNotebook -- only the page class type is TPage instead of TTabPage. However, if you look in DELPHI\DOC\EXTCTRLS.INT for the type declaration for TPage, you won't find it. For some reason, Borland did not include the TPage definition in the DOC files that shipped with Delphi. The TPage declaration *IS* in the EXTCTRLS.PAS unit that you get when you order the VCL source, right where it should be in the interface section of the unit. Here's the TPage information they left out: